qcs.ca: Capability Analysis

Description

Calculates the process capability indices cp, cpk, cpL cpU, cpm, cpmk for a qcs object and normal distribution.
Also, this function calculates confidence limits for C_p using the method described by Chou et al. (1990).
Approximate confidence limits for C_pl, C_pu and C_pk are computed using the method in Bissell (1990).
Confidence limits for C_pm are based on the method of Boyles (1991); this method is approximate and it assumes
the target is midway between the specification limits.
Moreover, calculates the process capability indices cnp, cnpk, cnpm, cnpmk for a qcs object.
A histogramm with a density curve is displayed along with the specification limits, a
Quantile-Quantile Plot for the specified distribution and contour graph is plotted for estimate the indice cpm.